OSLT is an acronym which stands for Or Something Like That. It apparently was invented by Woozle when writing letters in the 1990s or possibly earlier, though the first known documentation of it is email dialogue with Harena in 2001.
2007-04-10 Update: This has now morphed into saying "ocelot" instead of "OSLT". This variant was apparently coined by Tenebram (in #sluggysquad, 2006-01-11 16:50:08 EST), subsequently
overused a lot by Dhraakellian, and seems to have taken on a life of its own...
- My usage long predates the one cited in Urban Dictionary, but a thorough search of archived newsgroups from the 1980s may yet reveal earlier usage.
- Email, Woozle to Harena, 2001-02-23 23:00 "Spouting"